In the following description reference will be made to a lens, especially to an automatically darkening lens that is able to operate automatically to control transmission of light. The lens may be a light shutter type of a device that is able to control light transmission without distorting, or at least with relatively minimal distortion, of the light and the image characteristics carried by the light or represented by the light. Therefore, when a person looks through the lens, the image seen would be substantially the same as the image seen without the lens, except that the intensity of the light transmitted through the lens may be altered depending on the operative state of the lens. The lens may be used in a welding helmet, and the lens may be used in other types of devices, such as goggles, face masks, other types of helmets, etc. Such devices usually are employed to protect the face or the eyes of a person, as is known, for example, in the field of welding and in other fields, too.
For the purposes of providing eye protection, usually a welding lens provides light blocking characteristics in the visible, infrared and ultraviolet wavelength ranges. The actual ranges may be determined by the components of the lens, the arrangement of those components, and so forth. One example of a lens useful in accordance with the present invention is disclosed in copending, commonly owned U.S. patent application Ser. No. 08/105,734, filed Aug. 11, 1993, the entire disclosure of which hereby is incorporated by reference. The lens assembly disclosed in that patent application includes several liquid crystal cell light shutters, several plane polarizers, and a reflector or band pass filter, which is able to reflect ultraviolet and infrared electromagnetic energy and possibly also some electromagnetic energy in the visible wavelength range. The several liquid crystal cells, for example, may be birefringent liquid crystal cells sometimes referred to as surface mode liquid crystal cells or pi-cells.
Examples of liquid crystal cells, lenses using them and drive circuits are described in U.S. Pat. Nos. 5,208,688, 5,252,817, 5,248,880, 5,347,383, and 5,074,647 and in pending U.S. patent application Ser. No. 08/027,385 filed Feb. 17, 1993. In U.S. Pat. No. 5,074,647, several different types of variable polarizer liquid crystal devices are disclosed. Twisted nematic liquid crystal cells used in an automatic shutter for welding helmets are disclosed in U.S. Pat. Nos. 4,039,254 and Re. U.S. Pat. No. 29,684. Exemplary birefringent liquid crystal cells useful as light shutters in the present invention are disclosed in U.S. Pat. Nos. 4,385,806, 4,436,376, 4,540,243, 4,582,396, and Re. U.S. Pat. No. 32,521 and exemplary twisted nematic liquid crystal cells and displays are disclosed in U.S. Pat. Nos. 3,731,986 and 3,881,809. The entire disclosures of the patents and applications mentioned herein are incorporated by reference.
As is disclosed in several of the above patents, the respective shutters may have one or more operational characteristics (sometimes referred to as modes or states). One example of such an operational characteristic is the shade number; this is the darkness level or value of the shutter when it is in the light blocking mode. Another exemplary operational characteristic is the delay time during which the shutter remains in a dark state after a condition calling for the dark state, such as detection of the bright light occurring during welding, has ceased or detection thereof has terminated or been interrupted. Still another operational characteristic is sensitivity of the detection circuit and/or shutter to incident light, for example, to distinguish between ambient conditions and the bright light condition occurring during a welding operation. Even another characteristic, which may be considered an operational characteristic, is the condition of the battery or other power source for the shutter, such as the amount of power remaining, operational time remaining until the power source becomes ineffective, etc. In the past various of the operational characteristics of such shutters have been adjustable or fixed. However, relatively large devices were used to adjust and to display the values or settings of such operational characteristics, as by dials or knobs. It would be desirable to reduce the space required for such components and to improve the operability of them. It would be desirable to minimize the size and weight of such control and display components thereby to minimize size and weight of a welding lens or other automatic shutter device. Further, it would be desirable to facilitate manufacturing such automatic shutters.